A novel three-phase seven-level active clamped converter using H-bridge as a level doubling network

For the aim to increase level number and reduce switches number of multi-level converter, two half-bridge Power Electronic Building Blocks (PEBB) are inserted into the DC side of a typical three-phase H-bridge converter, a novel seven-level converter is proposed in this paper. By using the H-bridge as a level doubling network, the natural point voltage imbalance of traditional Natural-Point Clamped converter (NPC) is avoided. Moreover, because of the symmetrical structure, a reasonable control scheme for the DC voltage balancing is adopted, which based on ways of both active current superposition and switching states selection. Meanwhile, the frequency limitation to the switching states swapping is applied with a low-pass filter to ensure the control stable. The circuit operation and converter performance are analyzed. The analysis and control scheme is verified by MATLAB/SIMULINK simulation results.